Digital video can be transmitted from a source, such as a DVD player, video receiver, ATSC tuner, or other computer, to a display, such as a flat panel video monitor, using a protocol known as Digital Visual Interface (DVI). Having been developed primarily for computers, DVI does not provide for processing audio data.
Accordingly, to extend communication protocols to digital multimedia that includes audio for the purpose of, e.g., playing digital movies and the like, a protocol referred to as High Definition Multimedia Interface (HDMI) has been developed. HDMI is similar to DVI except it includes the use of audio as well as video data. Both DVI and HDMI are intended for wired transmission, and permit the encryption of digital multimedia using an encryption method known as High-Bandwidth Digital Content Protection (HDCP).
As recognized herein, to provide maximum placement flexibility and ease of installation, it may be desirable to present the multimedia on a display using a minimum of wiring. For instance, it may be desirable to mount a projector on the ceiling or to mount a plasma display or liquid crystal high definition (HD) television display on a wall, out of the way and capable of receiving multimedia data for display without the need for wires, since as understood herein among other things data transmission lines often do not exist in ceilings or walls.
The present invention further understands, however, that not just any wireless transmission system will do. Specifically, if a wireless link such as IEEE 802.11(b) is used that has a bandwidth which is insufficient to carry either compressed or uncompressed multimedia such as uncompressed high definition (HD) video, compressed multimedia standard definition (SD) video would have to be transmitted, requiring a relatively expensive decompression module at the projector. Some links such as IEEE 802.11(a) do have a bandwidth high enough to carry compressed HD video but not uncompressed SD or HD video. Also, in the case of 802.11(a) copyright protection maybe implicated because the link is sufficiently long range (extending beyond the room in which it originates) that it can be detected beyond the immediate location of the transmitting source. With this in mind, the present invention recognizes the need for a limited range, preferably directional, high bandwidth wireless link that is particularly suited for the short range wireless communication of uncompressed multimedia, particularly the rather voluminous genre of multimedia known as HD video.
Regardless of the particular application, the present invention makes the following critical observation. As understood herein, it is sometimes necessary for a master component (such as a microcontroller) in the source of data to read and write system information to a slave component (such as a register) in the display for control purposes using an appropriate protocol such as the I2C protocol used by DVI/HDMI. Typically, the master writes data to and reads data from register locations in the slave, and several slaves can be used, each with its own address. As an example, it might be necessary for a master in the source to write security information as might be related to the above-mentioned HDCP to one or more slaves in the display.
As further understood herein, it is desirable that reads and writes between master and slave occur in near real time, particularly in the case of encryption key exchange that is necessary to support decryption of video being played. The present invention critically recognizes that this is a challenge in wireless applications and in particular in effecting reads in wireless applications, because the read request must be transmitted across the wireless link from master to slave, acted on, and then requested data returned from slave to master over the link, potentially introducing unwanted latency.